@IntuitGabi   Just to be clear, the issue I am having is not associated with form 3800.  I am not even using that form on the entity I have the same problem with.  Mine is on a partnership return.  I do have a fair number of pdf attachments.  As a test I removed all of them and the error went away.  Then I added one back and the error came back.  So I don't think it is any one particular attachment.  Although I did not attach each of them individually to test it. 

Also, I have prepared a trust return today with one attachment and it is not giving me the error.  

Thank you for your help.